How to Size a New-Home Window Overhang for Summer Shade and Winter Sun

For a south-facing window, calculate a starting overhang depth as vertical gap ÷ tan(solar elevation), using the actual site, date, time and NOAA solar elevation. Compare a summer shade case with a winter-sun case, then widen the overhang beyond the glass to limit angled sunlight. This is a conceptual solar-control worksheet for schematic design—not structural sizing, energy modeling, a permit drawing or a universal rule.

The decision in this guide is narrow but consequential: can a fixed, horizontal projection above one proposed window do enough of the intended seasonal work to justify carrying it into the design? The answer depends on more than a familiar “one-third of the window height” rule. You need the window's orientation, the height of the overhang above the shade line, the sun's elevation and azimuth at the hours that matter, and the consequences of making the projection deeper or wider.

Use this page before design freeze, while the architect or designer can still move the window, change its size, adjust the wall, or select another solar-control method. The default jurisdiction is the United States. A local requirement in this article means the actual city, county, state, tribal or other authority having jurisdiction for the project; this guide does not identify a national permit exemption or a universal attachment rule.

1. Decide whether a fixed horizontal overhang is the right control #

A fixed horizontal overhang is a strong first candidate when the glass is close to south-facing and your main goal is to block high summer sun while admitting lower winter sun; it is a weak stand-alone candidate when the glass faces east or west, when low-angle glare matters, or when the projection would create unresolved structural, water or view problems. DOE describes passive solar design as using lower winter rays and deflecting higher summer rays, while PNNL identifies properly sized horizontal overhangs as especially effective for south-facing windows. DOE's consumer passive-solar guide and PNNL's shading guidance support that orientation-specific starting point.

The decision you should be able to make

At the end of the worksheet, you should be able to say one of four things for a specific window:

1. “Carry a fixed overhang forward for detailed design.”
2. “Carry it forward, but pair it with a shade, screen, fin, landscape element or other control.”
3. “Change the window's orientation, size, height or glazing specification before freezing the design.”
4. “Do not use this fixed overhang concept; ask the design team for another solar-control strategy.”

That is a design decision, not a promise that the finished room will have a particular temperature, energy bill, daylight level or number of hours in shade. An overhang can block direct rays while diffuse sky light, reflected light, heat conducted through the assembly, and solar heat admitted at the sides remain. DOE's daylighting guidance says window placement can provide light while protecting against glare and overheating, but it also notes that heat and glare are trickier to control on east- and west-facing windows. DOE Building Science Education's daylighting guidance is useful for that boundary.

What “south-facing” means for this worksheet

Do not decide orientation by the street address, the front elevation, or a rough visual impression. Record the outward-facing wall normal as a compass bearing: north is 0 degrees, east 90 degrees, south 180 degrees and west 270 degrees. Use the direction the exterior face points, not the direction you happen to view the drawing from. A wall 20 degrees east of true south is 160 degrees; a wall 20 degrees west of true south is 200 degrees. They are different walls for the side-angle and seasonal check, so never write “160 or 200” as interchangeable alternatives. NOAA reports solar azimuth clockwise from north, so a NOAA azimuth near 180 degrees is the sun being due south. NOAA's glossary and current calculator define the azimuth convention.

For a wall within roughly 30 degrees of true south, the seasonal logic may be a reasonable design hypothesis, especially if the window's important hours occur near the part of the day when the sun is in front of that wall. DOE's consumer guide recommends that passive-solar windows face within 30 degrees of true south and not be shaded during a stated winter daytime window, but that is general consumer guidance, not a requirement for your home or a guarantee of passive-solar performance. Read the DOE guide's orientation scope before treating that suggestion as a starting point rather than a specification.

Why east and west are an early warning

East and west windows see the sun near sunrise and sunset, when its rays arrive at a low angle relative to the wall. A shallow horizontal projection can therefore leave much of the glass exposed even if a section drawing appears convincing. PNNL says east- and west-facing windows may need deeper overhangs and another shading form, while north-facing windows can receive low-angle morning and evening sun for which vertical side shading is appropriate. PNNL's orientation-specific discussion is the reason this article does not offer one national width-to-depth rule for every façade.

This does not mean an east- or west-facing overhang is always useless. A deep porch, balcony or roof can shade for part of the day, and an overhang can protect from rain or support a larger architectural concept. The correct question is when it shades, which part of the glass it shades, what happens in spring and fall, and whether the remaining direct sun is acceptable. If late-afternoon glare in a west-facing office is the real problem, a movable exterior screen or interior shade may be more useful than adding a very deep fixed projection.

Originality brief

Current answers explain passive-solar orientation, generic overhang rules, window attachments and solar angles, but they are scattered between consumer guidance, practitioner material and a solar-position calculator. The missing decision is how one homeowner connects a real wall bearing, window geometry, shade line, target dates and hours to a comparison that can be checked by the design team.

The original contribution here is the “Source-linked seasonal overhang worksheet.” Method: preserve the raw site and solar-position inputs, use an explicit section formula for a south-facing conceptual case, compare at least two scenarios, and append the questions that geometry cannot answer. Limitations: the worksheet does not model the full sky, the building, the glazing product or the attachment. You can check it by reproducing the NOAA entries, recalculating the formula in degree mode, inspecting the section and plan drawings, and asking the architect, engineer, window specialist and authority having jurisdiction to review their respective parts.

Contribution record: Source-linked seasonal overhang worksheet

Method: Record latitude, longitude, time zone, wall azimuth, window dimensions and the vertical gap in feet; obtain solar azimuth and elevation for selected dates and times from NOAA; calculate the illustrative south-facing section depth as vertical gap divided by tan(solar elevation); compare at least two depths, then check side outflanking, glazing properties and project constraints.

Limitations: This is a conceptual solar-control screen, not structural, water-management, energy-model, permit or construction design. It does not model diffuse sky light, clouds, neighboring obstructions, reflected light, SHGC, VT, glare, occupant behavior, wind, snow, seismic loads, attachment capacity, local zoning, HOA rules or jurisdiction-specific permit requirements.

Stop conditions before you calculate

Pause the worksheet and hand the question to the design team if any of these are true:

• You do not know the wall bearing or cannot verify it from the site plan.
• The projection would attach to a wall, roof edge, window frame or cladding system whose load path has not been designed.
• The overhang would be high enough that future cleaning, inspection or repair creates a fall exposure.
• You are trying to use the worksheet to satisfy a local energy-code, egress, safety-glazing, wind, snow, wildfire, historic-district, coastal, floodplain or zoning requirement.
• The window is a skylight, sloped glazing, corner window or deeply recessed opening that does not fit a simple vertical-wall section.
• A neighbor, tree, utility, fence, grade change, porch, roof, screen or other obstruction changes the sun path.

The safest homeowner role is to collect dimensions, bearings, dates, priorities and photographs or site-plan references from a safe location. Do not climb onto a roof, fabricate a temporary overhang, drill into the wall, cut framing, move a window, or test a high exterior location for the purpose of validating this concept. A licensed design professional or qualified contractor in the project's actual jurisdiction must decide how a projection is attached and weathered.

2. Gather the inputs that make the comparison reproducible #

The worksheet is useful only when every input has a source, unit and person responsible for confirming it: the homeowner supplies priorities and site information, the designer confirms geometry, and the appropriate professional confirms structural, envelope and local-review implications. Record the raw inputs before doing any arithmetic so a changed window size or wall bearing does not silently invalidate the result.

Prerequisites and ownership

The prerequisite is a schematic drawing or window schedule that identifies the specific opening. You do not need permit-ready drawings to begin, but you do need enough information to distinguish one window from another. Create one row per window or per group of identical windows; do not average a south window and a southwest window into one row.

The time-zone entry deserves special attention. Use NOAA's current Solar Calculator, enter longitude using the international convention (east of Greenwich positive, west negative), and record the selected time zone and daylight-saving assumption. The current tool defines a time-zone value as the number of hours added to UTC to obtain local time; for example, U.S. Mountain Standard Time is UTC−7, so record -7, not +7. NOAA's time-zone table documents the convention. Save a screenshot, printout or copied record of the entries used. NOAA retains azel.html as an old courtesy calculator with longitude and time zone positive to the west; do not mix that old convention into a new worksheet. The old calculator's notice states the reversal explicitly.

Define the target shade line

“Shade the window” is not a complete requirement. Name the exact line you want the sun's direct ray not to cross. Common conceptual targets are:

• the bottom of the glass, if the goal is no direct beam on the whole glazed area at a selected summer time;
• the top of the glass, if the goal is to shade only the upper portion while accepting some lower-window sun;
• a sill, desk, seating area or interior floor line, if comfort or glare at a particular location matters more than uniform glass shade;
• the top of a second opening or a wall finish, if the projection is part of a façade composition.

For a homeowner comparison, use plain names such as “summer shade line = bottom of glass” and “winter-sun test point = bottom of overhang to bottom of glass.” Then draw those points on the section. If you change the target line, you change the vertical gap and therefore the calculated depth.

Measure horizontally and vertically, not along a slope

For the conceptual formula, depth is the horizontal distance from the relevant wall or glass reference to the outer edge of the overhang. Vertical gap is a plumb dimension between the bottom of the overhang and the target shade line. Do not measure the overhang along a sloped roof plane or use a diagonal tape measurement as if it were depth. PNNL's worked example specifically distinguishes a level horizontal depth and a plumb vertical height, including the depth from the glass rather than casually from the wall or frame. See the measurement definitions in PNNL's shading guide.

Keep the reference consistent. If the overhang has a gutter, fascia, trim, screen, photovoltaic panel or other edge that affects the ray, record which physical edge you use. If the shading plane is not horizontal, record the slope and stop treating the simple formula as exact. Your architect can convert the concept into the actual section and decide which edge controls the geometry.

Establish the homeowner's priorities before optimizing

Write down the priority in order, because “maximum shade” and “maximum winter sun” are often competing goals. A south living-room window might prioritize summer comfort, winter daylight, a view, no moving parts, rain protection, a narrow façade, or low construction complexity. A west bedroom might prioritize late-day glare and cooling more than winter solar heat. A north bathroom might need privacy and diffuse light, making a fixed overhang a poor answer to the actual problem.

Use a short brief for each opening:

The brief becomes the test for the next decision. If a design passes the geometric section but fails the view, drainage or attachment priority, it has not passed the homeowner's decision.

3. Use NOAA solar position to build the seasonal test cases #

Use NOAA solar azimuth and elevation for the actual site, local date and clock time that represent the homeowner's summer and winter priorities; never substitute latitude alone for a time-of-day solar position. NOAA defines elevation as degrees above the horizon and azimuth as degrees clockwise from north, which gives the two angular inputs needed to decide whether a south-facing section is representative and when a ray will arrive from the side. NOAA's glossary for the current calculator should travel with the worksheet.

Choose test dates that answer the decision

There is no universal pair of dates that captures every family's comfort problem. Choose dates tied to the design question, then add a small set of stress cases. A useful starting set might include:

• a summer solstice or a representative hot-season date;
• the earliest and latest summer hours when the room is occupied;
• an equinox or shoulder-season date if spring or fall overheating is a concern;
• a winter-solstice or representative cold-season date;
• the winter hours when direct sunlight is wanted in the room;
• a late-afternoon west-glare case or early-morning east-glare case when orientation demands it.

Label dates as local civil dates and times, not “solar noon” unless you have deliberately selected solar noon. A clock-time requirement such as “shade at 3:00 p.m.” can correspond to a different solar angle than a requirement stated as “two hours after solar noon.” Both can be valid; they answer different questions.

Enter the location and preserve the time convention

On NOAA's current calculator, enter the project's actual latitude and longitude, with west longitudes negative, then select or verify the project's named time zone and UTC offset. Enter the local civil date and time, record whether daylight saving is active, and copy the solar azimuth and elevation. The current calculator is not actively supported or maintained, so record the access date and treat the result as a reproducible planning input rather than a construction tolerance. NOAA also warns that time-zone and daylight-saving settings can be inaccurate for some dates and that atmospheric conditions and algorithm uncertainty can make observed values differ. Use NOAA's current calculator and its limitations.

Do not “correct” NOAA's azimuth into a wall-relative angle by eye. Keep both fields:

• wall azimuth: direction the wall faces, clockwise from north;
• solar azimuth: direction to the sun, clockwise from north;
• azimuth difference: the smaller horizontal angle between them.

For an east-facing wall, the important morning sun may be near the wall's normal direction; for a west-facing wall, the important afternoon sun may be near it. For a south-facing wall, a near-180-degree solar azimuth is the cleanest section case. As the difference grows, the ray arrives more obliquely and can bypass the sides of a narrow overhang even if the vertical section remains unchanged.

Select a summer shade case and a winter-sun case

At minimum, select one summer case and one winter case for the opening. Write the desired result beside each:

The word “pass” needs a tolerance. A conceptual study might mark a case as “passes at the exact selected hour” or “passes with a 30-minute margin,” but do not imply the margin is a code tolerance or an energy guarantee. The more sensitive the room is to glare or cooling, the more times you should test and the more useful a three-dimensional study becomes.

A modeled example of the input record

The following values are illustrative, not a measurement of a real site. They show the record format and arithmetic only. Replace every solar-position value with the NOAA output for the project's actual coordinates and selected local times.

The example deliberately includes a large vertical gap so the arithmetic is visible. A real overhang that is only a foot above the top of a five-foot window would use a much smaller gap to the top of glass, but a full-window shade line at the bottom of glass would still use the entire distance from the overhang underside to the bottom of glass. Never choose the smaller dimension merely because it produces a more convenient projection.

4. Calculate conceptual depth in a south-facing vertical section #

For a south-facing vertical section in which the sun is treated as arriving in the plane normal to the wall, calculate the starting depth as D = V ÷ tan(θ), where D is horizontal overhang depth in feet, V is the vertical gap in feet from the overhang underside to the target shade line, and θ is solar elevation in degrees. This is the transparent geometry bridge in the worksheet, not a structural design and not a complete three-dimensional shading model.

Draw the geometry before trusting the formula

Draw the wall as a vertical line. Mark the target shade line, the window and the bottom of the overhang. Draw the vertical gap V between the target line and the underside of the overhang. From the outer edge of the overhang, draw the sun ray toward the target line. The right triangle has:

• opposite side = V;
• adjacent side = D;
• angle at the target line = solar elevation θ;
• relationship = tan(θ) = V ÷ D;
• rearranged depth = D = V ÷ tan(θ).

Use degree mode in the calculator. A spreadsheet formula is =V/TAN(RADIANS(theta)) in systems that expect radians inside the tangent function. A handheld calculator may have a degree/radian setting. Confirm the result with a scaled section drawing; if the formula and drawing disagree, check the angle mode, the vertical reference and the meaning of “depth.”

The direction of the inequality matters. To block the selected summer ray from reaching the target line, the overhang depth must be at least the calculated conceptual value: D >= V ÷ tan(θ_summer). To allow the selected winter ray to pass the target line, the depth must be less than the analogous boundary for that winter ray: D < V ÷ tan(θ_winter), assuming the same south-facing section and target geometry. This section-and-angle approach follows the wall, glazing, summer-angle and winter-angle construction illustrated in DOE's passive-solar overhang sizing guidance. Because the winter elevation is usually lower, its boundary is usually larger. That creates a useful interval only if the selected seasonal angles and target lines actually support one.

Apply the calculation to the illustrative summer case

Use the illustrative values V = 6.0 ft and θ_summer = 57°:

D_summer >= 6.0 ft ÷ tan(57°)

D_summer >= 6.0 ft ÷ 1.540

D_summer >= 3.90 ft

Rounded for a conceptual comparison, Scenario A needs at least 3.9 ft of horizontal depth to block that selected summer ray at the bottom-of-glass shade line in the idealized south-facing section. This does not mean a 3.9-ft built projection will shade the whole window all day. The example summer azimuth is 205 degrees rather than exactly 180 degrees, so side outflanking must be checked in plan, and other times have different elevation and azimuth.

Apply the winter pass condition

Use the same vertical gap and the illustrative winter elevation θ_winter = 31°:

D_winter boundary = 6.0 ft ÷ tan(31°)

D_winter boundary = 6.0 ft ÷ 0.601

D_winter boundary = 9.98 ft

In this simplified section, a depth of 3.9 ft would be below the roughly 10.0-ft boundary, so the selected lower winter ray can pass to the bottom-of-glass target line. A depth of 11 ft would fail that winter pass test in the same idealized geometry because the overhang would intercept the ray before it reaches the target. The result is not “winter sun guaranteed”; it is “this selected winter ray is geometrically allowed by this section assumption.” The ray may still be blocked by a side wall, screen, tree, neighboring building, upper story or interior shade.

Compare two depths, not one magic number

The point of the worksheet is comparison. Keep the raw numbers visible:

Scenario B is not “the answer.” It is a candidate that deserves the next checks. Scenario C may be appropriate if a porch is already desired and the structure, drainage, daylight and view work. Scenario A may be acceptable if summer shading is supplemented by an exterior screen. Scenario D may be appropriate only when the homeowner intentionally prioritizes permanent shade over winter direct sun. A transparent comparison keeps those value choices visible instead of disguising them as a formula result.

Test sensitivity to the solar elevation

The tangent relationship is sensitive at low solar elevations. Holding V = 6.0 ft constant gives this conceptual sensitivity table:

These are arithmetic outputs for the stated formula, rounded for readability. They show why a low-angle east or west case can demand an impractically deep horizontal projection, and why a depth selected at a high summer elevation may not control an earlier or later hour. They do not show the effect of azimuth, overhang width, wall thickness, glazing, clouds, reflections or obstructions.

Change the target line and recalculate

Suppose the same illustrative window has its overhang underside 1.0 ft above the top of glass. For a 5.0-ft-high window, the gap to the top-of-glass line is V = 1.0 ft, while the gap to the bottom-of-glass line is V = 6.0 ft. At 57 degrees:

• top-of-glass target: D >= 1.0 ÷ tan(57°) = 0.65 ft;
• bottom-of-glass target: D >= 6.0 ÷ tan(57°) = 3.90 ft.

Those are not contradictory answers; they answer different shade questions. A shallow projection can shade the upper edge while direct sun still reaches the lower window and floor. If the homeowner says “I want the room comfortable” rather than “I want every square inch of glass shaded,” the design team should test the interior sun patch, glare and glazing rather than force a whole-window target that creates an unwanted roof form.

Know when the section is not valid

The simple formula is a useful south-facing vertical-screen calculation when the relevant solar ray lies close to the section plane. It becomes incomplete when:

• the solar azimuth differs materially from the wall normal;
• the window is near a corner or side wall;
• the overhang has a side wall, fin, beam, gutter or sloped surface that changes the edge;
• the sun must be blocked at more than one point or more than one hour;
• the target is an interior floor, desk or seating position rather than a wall line;
• nearby buildings, trees, terrain or a second story block or reflect light;
• the façade is not vertical or the overhang is not level.

In those cases, preserve the section calculation as a traceable starting point, but ask the architect or energy-modeling professional for a three-dimensional sun-path, shadow or daylight study. A more elaborate tool is not automatically more accurate if the wall bearing, site coordinates, time convention or window geometry are wrong.

5. Size width and side extensions for angled sun #

Make the overhang wider than the window whenever the goal is meaningful shade, because angled sun can go around an edge even when the section depth passes. PNNL says south-facing overhangs should extend on both sides and gives a south-facing rule of thumb of side extension at least equal to the height from the bottom of the window to the bottom of the overhang, while also warning that early and late sun can still outflank the projection. Use PNNL's side-extension guidance as a starting heuristic, not as a universal specification.

Record three different widths

Homeowners often use “overhang width” to mean three different dimensions. Separate them:

1. window width: the clear or glass width being evaluated;
2. side extension: the amount the shading plane extends beyond the window on one side;
3. total overhang width: window width plus both side extensions, measured on the same reference line.

For a symmetric south-facing starting case:

total width = window width + left extension + right extension.

If the 6.0-ft illustrative window uses a 6.0-ft side extension on each side, the conceptual total width is 6.0 + 6.0 + 6.0 = 18.0 ft. That may be far too large for the actual façade, which is exactly why the rule should trigger a three-dimensional check rather than be copied without judgment. PNNL's published example uses a 3-ft by 3-ft window and a 0.5-ft rise above the window to illustrate a total width of about 10 ft under its rule of thumb; it explicitly notes that early and late sunlight can still outflank even that width. Review the example and its scope.

Choose the correct side for an east or west wall

For a west-facing window, late-day sun approaches from the south side of the façade relative to the wall view. PNNL describes extending a west-facing overhang toward the south, which appears to the outside viewer as the right side; on an east-facing wall, the southward extension appears on the left. PNNL explains the orientation of those one-sided extensions.

Treat that as a plan-drawing instruction, not a cue to memorize left and right. Draw north on the site plan, draw the wall, draw the sun azimuth for the selected hour, and see which edge the ray would bypass. If the window is in a corner, the adjacent wall may shade one side at some hours and worsen the view or wind exposure at others.

Use azimuth difference to find the side-angle stress case

For each test time, calculate the smallest difference between the wall azimuth and solar azimuth. Mark the largest difference among the hours you care about. That is a candidate side-angle stress case. The section formula still tells you something about the vertical interception, but it cannot tell you whether the ray passes around the left or right edge. A plan sketch with the window, overhang rectangle and sun direction is the minimum useful companion.

You can make the plan check more informative without pretending it is a full solar simulation:

• draw the overhang to the proposed total width;
• draw the wall line and window opening to scale;
• draw a ray from the sun direction toward the window;
• mark which glass is hidden by the projection and which glass is visible around an edge;
• repeat for the selected morning, midday and afternoon cases;
• record “full shade,” “partial shade,” or “outflanked,” rather than a false percentage unless a qualified model produces one.

The farther the sun is from the wall normal, the more valuable the width and plan check become. A narrow overhang can be effective for a near-south midday case and ineffective one hour later. If the homeowner's problem is a narrow glare window, size for that window of time or choose an operable control rather than imposing the largest projection on the entire elevation.

Balance shade against view and daylight

A deeper or wider projection can reduce direct sun but may darken the upper part of the room, change the exterior proportion, interrupt a view, collect leaves or snow, and complicate cleaning. PNNL lists multiple solar-control methods—glazing, landscaping, architectural shading, exterior attachments and interior attachments—so an overhang is one part of a control set rather than the only lever. See the PNNL solar-control options.

The right question is not “How big can the overhang be?” but “What is the smallest fixed geometry that meets the stated priority with an acceptable side effect?” If the answer is “no fixed geometry does,” record that conclusion. It can prevent a late change order in which the builder is asked to attach an unplanned projection to a wall that was never designed for it.

6. Account for glazing, glare and controls beyond geometry #

Treat the overhang as one solar-control layer and coordinate it with glazing and adjustable shades; geometry alone does not determine how much heat or light enters the room. DOE defines SHGC as a measure of solar heat transmitted through a fenestration product and VT as visible-light transmission, while PNNL describes operable attachments as a way to adjust heat gain, daylight and view. DOE's window-selection guidance and PNNL's attachments guidance provide the handoff basis.

Add the actual window product to the worksheet

Do not write “energy-efficient glass” in the record and assume the design question is closed. Ask the window supplier or designer for the actual product's:

• whole-product or certified SHGC, with the product and configuration identified;
• visible transmittance, or VT;
• U-factor where heating performance matters;
• frame, sash, spacer and glass configuration;
• exterior or interior attachment assumptions used in any energy analysis;
• operability and cleaning requirements;
• installation and flashing interface expected by the window and wall system.

Lower SHGC generally means less solar heat transmitted through the product, but DOE also notes that VT measures visible light and that the two should be considered together. A low-SHGC choice may reduce heat gain while also changing daylight or appearance; a high-SHGC choice may be intentional in a cold-climate strategy but could increase cooling or glare concerns. Use DOE's SHGC and VT definitions, then let the designer reconcile them with climate, orientation, room use and the project's energy targets.

Do not infer from SHGC that the overhang can be made smaller without checking the whole system. SHGC is a product characteristic; the overhang controls direct rays at selected geometry. A window with a low SHGC can still create discomfort from visible glare or a bright sun patch, and a window with a higher SHGC can be comfortable if shading, orientation and interior design work together. The worksheet should record both the geometry decision and the unresolved product decision.

Separate direct-beam shade from glare control

Direct-beam shade and glare are related but not identical. A ray can miss the glass while the sky remains bright, or the glass can be shaded while a bright neighboring roof reflects light into the room. DOE says careful window placement can protect from glare and overheating, and that north and south façades are easier to control than east and west façades. Read the DOE daylighting scope.

For each room, write a visual-comfort test in plain language:

• Will direct sun strike a screen, monitor, kitchen counter, bed or seating position?
• Is the problem all-day brightness, a narrow bright beam, reflected glare or radiant heat on occupants?
• Does the room need the view at the same time that it needs shade?
• Can an occupant adjust a shade, or must the control be automatic?
• Is winter direct sun desired for warmth, daylight or both?

If the room needs an adjustable answer, fixed geometry may be only the first layer. PNNL says static systems such as roof overhangs or trees are not easily adjusted, while shades, blinds, shutters and similar attachments can be operated to optimize heat gain, natural light and view. PNNL's operability discussion supports recording the control behavior as part of the design brief.

Decide whether exterior or interior control belongs in the concept

Exterior control generally intercepts sunlight before it reaches the glass, while an interior shade can be adjusted for privacy, view and glare. This article does not assign a universal performance advantage to one product because the product, climate, attachment, window and operating behavior matter. Ask the design team to compare:

PNNL notes that attachments can complement an exterior overhang when the overhang shades the upper part but lower-angle sun reaches the lower window. The PNNL attachment example gives the design team a useful way to discuss partial rather than all-or-nothing shade.

Do not use a fixed overhang to solve a different problem

If the concern is winter heat loss at night, an overhang is not the primary control; consider the window's U-factor, air leakage, interior shade behavior and envelope detailing with the design team. If the concern is summer heat from a skylight, a vertical-wall section is not the right geometry. If the concern is a privacy view from a neighbor, a projection may change brightness without solving sightlines. If the concern is rain, the projection needs a water-management detail, not just a sun-angle number.

DOE lists cost, aesthetics, structural capability, water resistance, durability, maintenance, sound control, ventilation, thermal comfort, fading and glare control among window-selection considerations. Those DOE considerations belong in the handoff because a solar-control win can become a building-envelope problem if the rest of the assembly is ignored.

7. Hand the concept to the right professionals and jurisdiction #

Hand the worksheet to the architect or designer first, then route separate questions to the structural professional, window supplier or fenestration specialist, energy-modeling professional and the actual authority having jurisdiction; no one worksheet result authorizes construction. PNNL's guidance is planning guidance, and DOE's passive-solar material does not establish structural, permit or local attachment requirements. DOE's passive-solar factsheet explicitly limits its responsibility, which is an important boundary for a homeowner handoff.

What the homeowner owns

The homeowner is responsible for decisions about comfort, view, daylight, desired winter sun, acceptable fixed elements, seasonal operation and budget priorities. You can safely prepare:

• the room-by-room priority brief;
• the site coordinates and a source or confidence note;
• a verified or provisional wall bearing;
• the window schedule and the intended target shade line;
• the selected summer, winter, shoulder-season and side-angle cases;
• NOAA output records and the arithmetic;
• notes about trees, neighboring buildings, fences, grades and future additions;
• questions about cleaning, maintenance, privacy and operation.

Do not turn a conceptual measurement into a field instruction. A tape measurement from the ground can inform the design, but it does not establish the capacity of a wall, roof edge, window frame or cladding system. Do not order a custom projection from the worksheet alone.

What the architect or designer owns

Ask the architect or designer to confirm the wall azimuth, the true window geometry, the vertical reference, the overhang edge, the interior target and the hours that should be studied. They should place the concept on the plan, elevations and sections, coordinate it with rooflines, eaves, porches, adjacent windows, exterior doors and views, and decide whether a more complete solar or daylight study is warranted.

Give them the worksheet with the raw and derived fields separated. The raw fields are coordinates, dates, times, wall bearing, window dimensions and NOAA outputs. The derived fields are depth thresholds, scenario results, side-extension heuristics and pass/fail labels. That separation makes it easy to revise the calculation if the window moves 18 inches or the designer changes the overhang underside.

What the structural professional owns

The structural professional must determine the load path, member sizes, connections, support conditions and applicable design loads for the actual projection and building. The worksheet intentionally does not estimate those items. A deep overhang can be a roof, deck, canopy, trellis, porch or attachment with different geometry and loads; even a visually light shade may need support, bracing and connection detailing.

The professional must also coordinate penetrations and attachment locations with the wall, roof, cladding, air barrier, water-resistive barrier, insulation and window flashing. A homeowner should not infer that “solar shade” means “nonstructural.” The correct next action is to give the structural concept to the design team before the wall assembly and framing are frozen.

What the window or envelope specialist owns

Ask the window supplier or envelope professional to confirm the product ratings, flashing and sill conditions, attachment clearances, cleaning access and compatibility between the proposed projection and the window/wall system. The supplier should identify the exact product and configuration, not just an approximate SHGC or a generic “low-E” description. DOE explains that low-emissivity coatings, glazing layers, frames and other product features affect window performance, and that installation practices matter for air infiltration. Use the DOE product guidance for the questions to carry forward.

The envelope review should answer practical questions the sun triangle cannot:

• Where does water go at the wall-to-overhang intersection?
• Does the projection shed water onto the window, siding, walkway or a lower roof?
• Can leaves, snow or ice accumulate at the edge?
• Can the window be replaced without removing the projection?
• Can sealants, membranes and flashings be inspected and renewed?
• Does the projection block a required opening, emergency access path or maintenance route?

The answers belong in drawings and specifications, not just in a homeowner's spreadsheet.

What the authority having jurisdiction owns

Ask the building department, planning department, zoning office, historic-district authority, HOA or other governing body that actually applies to the project which reviews are required. Identify the jurisdiction by name in the project record—for example, “City of ___ Building Division,” “___ County Planning Department,” or the applicable tribal, state or federal land authority. This article does not claim that an overhang is exempt from a permit, setback, lot-coverage, height, historic, fire, coastal, stormwater or design review.

The questions to ask are:

• Does the proposed projection require a building permit in this jurisdiction?
• Is it counted as floor area, lot coverage, a projection, a porch, a canopy or another defined element?
• Does it affect setbacks, height limits, easements, sight triangles or property lines?
• Are there wind, snow, seismic, wildfire, coastal or floodplain requirements that change the design review?
• Does the jurisdiction require sealed drawings or a licensed design professional's calculations?
• Does an HOA, condominium association or historic authority impose another review?

Record the answer, contact, date and document or webpage used. A local rule remains local. Do not rewrite it in the article or project brief as a national rule.

The builder's role is coordination, not invention

Once the design team has selected a concept and the required professionals have resolved it, the builder can price and sequence the actual work. Ask the builder to identify what is included in the base scope: framing, waterproofing, flashing, gutters, soffits, screens, paint, electrical controls, access equipment, maintenance provisions and inspection coordination. If an overhang is added after the wall package is priced, require a written scope and responsibility matrix.

The builder should not be expected to choose a structural connection or quietly substitute a narrower projection because the original is difficult. A change that affects the solar geometry should return to the architect/designer for a new section and plan check. A change that affects load path or envelope should return to the appropriate professional. This is the handoff chain that prevents a successful schematic idea from becoming an undocumented field improvisation.

8. Verify the decision before design freeze #

Verify the concept by reproducing the inputs, checking both section and plan geometry, comparing at least two scenarios, reviewing glazing and glare, and documenting the responsible professional's response; only then decide whether the overhang is carried into the next drawing set. Verification means the record is coherent and reviewable, not that a calculator has guaranteed future shade or energy savings.

The pre-freeze verification checklist

Use this checklist for each opening:

• The room and window identifier are unique.
• Latitude and longitude are recorded with their source and confidence.
• Time-zone and daylight-saving assumptions are recorded.
• Wall azimuth is stated as a bearing clockwise from north.
• Window width and height are in feet, with the reference identified as clear opening, frame or glass.
• Window sill and head elevations use the same datum as the overhang underside.
• The target summer shade line is named and drawn.
• The target winter entry point is named and drawn.
• At least one summer and one winter date/time have NOAA azimuth and elevation records.
• A shoulder-season or orientation-specific stress case is included where relevant.
• The section formula was calculated in degree mode and checked on a scale drawing.
• At least two overhang depths are compared with the same inputs.
• Left extension, right extension and total width are recorded separately.
• A plan check identifies which rays outflank the sides.
• The actual proposed window's SHGC and VT are requested or marked unknown.
• View, glare, daylight, rain, snow, leaves and cleaning consequences are recorded.
• The architect/designer has reviewed the concept and identified whether a 3-D study is needed.
• The structural professional has been assigned attachment and load-path review.
• The window/envelope professional has been assigned flashing, drainage and replacement review.
• The actual authority having jurisdiction has been identified for permit and zoning questions.
• The builder's scope will not proceed until the reviewed detail is in the contract documents.

A decision matrix for common outcomes

Verify source and arithmetic integrity

Perform a simple audit before a meeting:

1. Open the current NOAA Solar Calculator and reproduce one summer and one winter entry.
2. Confirm that latitude sign, west-longitude sign, UTC offset and daylight-saving setting were not transposed; do not use the old west-positive convention by accident.
3. Confirm that the solar elevation is above the horizon for the selected time.
4. Confirm the wall azimuth and solar azimuth use the same north-based convention.
5. Recalculate V ÷ tan(θ) in degree mode.
6. Check that the depth is horizontal and the gap is vertical.
7. Compare the calculated threshold with the drawn section.
8. Draw the overhang width in plan and test the largest relevant azimuth difference.
9. Mark every assumption that is not yet verified.

NOAA itself says the current calculator is no longer actively supported and notes uncertainty from atmospheric conditions and algorithms, so a result should not be presented as an observed shadow boundary with construction-level precision. Keep NOAA's current limitation notice attached to the record. If the decision turns on a narrow 15-minute comfort window, a few inches, or a difficult façade, that is a signal to commission a more complete study rather than to add false precision to the spreadsheet.

Verify the professional handoffs

Ask for a response to each assigned question, not a general “looks good.” The architect or designer should mark the selected depth and width on the relevant drawing. The structural professional should identify the support and attachment concept. The envelope professional should identify flashing, drainage and maintenance provisions. The window supplier should confirm the actual product values. The named local jurisdiction should answer its own permit or zoning question.

Keep the response with the project record. A verbal statement can be useful during a meeting, but the next drawing set, specification or written email should capture the decision that affects price or construction. If the professionals disagree, do not average their answers. Return to the unresolved input or ask the lead designer to coordinate the conflict.

Common failure cases and recovery

Failure: using a rule of thumb without a site

A remembered ratio such as “one foot of overhang for every two feet of glass” hides the latitude, hour, wall bearing, vertical gap and target line. Recovery: keep the rule only as a rough scenario, then replace it with actual NOAA solar positions and the explicit section calculation.

Failure: measuring from the wrong reference

Measuring from the outside face of the wall when the effective shading edge is at the glass, or measuring along a roof slope, changes the triangle. Recovery: draw the wall, glass, overhang underside and outer edge; label every horizontal and vertical dimension.

Failure: calculating one midday hour

A design can pass at solar noon and fail at the occupied hour that causes glare. Recovery: add beginning, middle and end times for the summer concern, then a shoulder-season and winter case. Use plan checks for side angle.

Failure: treating a west window like a south window

The section may look persuasive, but low-angle afternoon rays can outflank a shallow or narrow projection. Recovery: test the actual wall bearing and late-day solar azimuth; compare a movable exterior control or another façade strategy.

Failure: making the overhang as wide as the glass

Side-angle rays can bypass the edge. Recovery: record side extensions separately, use PNNL's heuristic only as a starting point, and draw the plan at the chosen hours.

Failure: assuming shade equals comfort

A shaded pane can still admit diffuse light or reflected glare, and an unshaded pane's effect depends on SHGC, VT, room use and interior conditions. Recovery: define the actual comfort symptom and add product and interior-view questions.

Failure: assuming a low-SHGC window makes geometry irrelevant

Window properties change solar heat transmission but do not erase direct-beam glare, view or the façade's water and structural issues. Recovery: coordinate SHGC and VT with the overhang study rather than substituting one for the other.

Failure: designing the attachment after the wall is fixed

An attractive projection can arrive after the framing, cladding, flashing and window schedule are already committed. Recovery: carry a conceptual attachment zone into schematic design and assign structural and envelope review before design freeze.

Failure: treating NOAA output as a field observation

Solar-position output is a repeatable planning input, not a guarantee of a visible shadow under every atmospheric condition. Recovery: retain the current calculator's unsupported-tool and atmospheric caveats, record the longitude/time-zone convention, and use a model or professional review when the margin is narrow.

Failure: assuming a permit answer from another place

A projection rule in one city, county or HOA does not establish the rule in another. Recovery: name the actual authority having jurisdiction and ask about this address, this projection and this stage of design.

Failure: trying to validate the concept from a roof

Climbing, drilling, temporary loading or accessing an unfinished edge introduces hazards unrelated to the solar calculation. Recovery: use drawings, safe ground-level observations and qualified professionals for height, structural, electrical or envelope work.

Decide what happens next

If the record passes the conceptual checks, the next decision is not “build it.” It is “which reviewed design option goes into the next drawing set, and what must be resolved before pricing?” Put the selected scenario, rejected scenarios, raw inputs, evidence links, assumptions and open questions into the project brief. Give the designer a clean copy and ask for a revised section and plan. This package has no already-published topical /build/design guide to link yet, so use Brictale's homeowner Blog for the current collection and replace that broad continuation with a specific published design route when one exists.

If the record fails, that is also useful. A rejected fixed overhang can lead to a smaller projection plus exterior screen, a different window orientation, a revised window size, a new glazing selection, a porch that solves several goals, a landscape strategy, or no added shading at all. Record why the concept failed—summer depth, winter obstruction, side outflanking, glare, view, water, structure, maintenance or local review—so the same option is not re-proposed later without new information.

The homeowner's final pre-freeze note can be short:

For window [identifier], we tested [dates/times] at [coordinates] using [time-zone assumption]. The selected conceptual option is [depth] ft deep and [left/right/total width] ft wide, with [target shade line]. It [passes/fails] the stated section cases and [passes/fails] the plan outflanking checks. Remaining owners are [designer], [structural professional], [envelope/window professional] and [named authority having jurisdiction]. No construction or procurement is authorized by this worksheet.

That note preserves the decision boundary. It gives the next professional enough information to verify the concept, exposes the tradeoffs the homeowner actually chose, and keeps a transparent solar-control calculation from being mistaken for a permit-ready or construction-ready design.